The present invention relates to a valve which includes an actuator for moving a value plunger to shut or open a port.
As shown in FIG. 4, in a conventional fuel injector disclosed in Japanese Patent Unexamined Publication No. 59-165858, the fuel injector 100 includes an injection valve 110 for injecting high-pressure fuel and a three way electro-magnetic valve 120 for operating the injection valve 110 to control injecting-timing and the volume of the injected fuel.
The injection valve 110 has a first body 113 including a fuel supply path 111 and a pressurized chamber 112. And the first body 113 contains a hydraulic piston 114 connected mechanically to a nozzle (not shown in FIG. 4).
The three-way electro-magnetic valve 120 has a coil 126, a housing 127, a spacer 128 and a second valve body 124 including a first path 121, a second path 122 and a third path 123. The second valve body 124 contains a valve 125 which causes the second path 122 to communicate with the first path 121 or alternatively with the third path 123.
In the fuel injector 100, when the second path 122 is caused by the valve 125 to communicate with the first path 121, the high-pressure fuel flows from the fuel supply path 111 to the pressurized chamber 112 through the first path 121, the valve 125 and the second path 122 so that the pressure in the pressurized chamber 112 becomes high. When the increased pressure in the pressurized chamber 112 presses the hydraulic piston 114 downwardly to operate the nozzle, the nozzle is kept at its closing position.
When the second path 122 is caused by the valve 125 to communicate with the third path 123, the high-pressure fuel is discharged from the pressurized chamber 112 through the second path 122 and the third path 123 so that the pressure in the pressurized chamber 112 becomes low and the hydraulic piston 114 returns upwardly and the nozzle is moved to its open position for injecting the high-pressure fuel.
The injection valve 110 and the three-way electro-magnetic valve 120 contained by a tube-shaped member 140 are tight contacted with each other by an axial force generated by a retaining nut 130 which engages with the tube-shaped member 140 and is driven home thereon, so that fluid communications between the fuel supply path 111 and the first path 121 and between the pressurized chamber 112 and the second path 122 are securely maintained with no leakage therefrom.
In the conventional valve described above, since the housing 127 and the spacer 128 are transformed by the axial force, it is difficult to maintain the movable range of the valve 125 and air-gap 129 at respective desired degrees. Therefore, the three-way electro-magnetic valve 120 can not operate in a stable manner.